A mobile accessory that lets you communicate without cell service has taken off with Bitcoin enthusiasts, in part because it prevents spying eyes.Photo by GoTenna

Daniel Levy, a Web developer living in the Puna District of Hawaii, lived through a 12-day blackout after a rather vicious hurricane earlier this summer. Many residents in his community were stuck powerless until the local utility company restored the grid, while some subsisted on solar energy. It was after that, Levy said, that he sought a solution and came upon GoTenna.

The gadget -- a small Bluetooth-enabled rod packed to the brim with modern radio innards -- lets you create your own private, secure communication network for sending messages without cell service using your smartphone. Though marketed toward outdoors and emergency situations like hiking and disaster relief, GoTenna is getting a boost from the cryptography community. Levy, whose neighborhood gets little to zero reliable cell service, happens to represent both. He's among the more than 25 percent of GoTenna preorder customers who paid for the product with the cryptocurrency Bitcoin.

"We do not need to be dependent on centralized industries for our communication, which is a very important part of our modern lives," Levy told CNET. The developer runs WebOfTrust.net, a peer-to-peer credit and collaboration-focused social network currently in development that aims to take the decentralization and financial empowerment elements of Bitcoin and apply them to his local community in Hawaii. He's considering integrating with GoTenna using the company's software development kit (API) to link the gadget with his Web platform.

"With GoTenna, we can create our own, decentralized mesh network that we own, and be in control of the data that we create," he said. Levy said he wouldn't have purchased GoTenna had the company not accepted Bitcoin as payment, nor if the device's communication lines had not been end-to-end encrypted and the messages never stored, he said. "If it proves to be useful, I would like to encourage my community to start utilizing these devices."

Chatting in dead zones, from Burning Man and beyond

GoTenna, which began taking preorders for pairs of its off-the-grid communication device in July to ship this fall, represents a unique blend. Its product mixes everyday consumer needs with the modern, more niche necessities of Web-savvy users who rely on encryption to navigate our increasingly spying- and risk-fraught communications technology.

While a novel accessory, GoTenna's multipurpose functionality is popping up more and more, especially in software. Mobile apps like FireChat and the Serval Mesh let users create mesh networks -- a way to rig together smartphone communication links via Bluetooth, like daisychaining USB or Ethernet cables -- for communicating without cell service as well, though at far shorter ranges. GoTenna, which does not use mesh networking technology and instead sends messages on a distinct and separate radio wave frequency, works up to 50 miles at high elevations and nine miles in most outdoor scenarios.

The promise of mesh networking with devices like GoTenna, pictured above, is the ability to take control of communication links and rely less on companies.Photo by Screenshot by Nick Statt/CNET

FireChat's developer, OpenGarden, regularly orchestrates campaigns to get FireChat up and running at events like large-scale music festivals and off-the-grid retreats like Burning Man. Yet all the while FireChat also offers encryption enthusiasts a tool for speaking beyond the eyes of Verizon, Google or the National Security Agency.

Point the finger at whistle-blower Edward Snowden's bombshell NSA leaks last year or at the seemingly never-ending onslaught of hacks threatening our largest institutions and retail stores. Whichever is sending the loudest message, it's now clear that encryption is no longer something reserved for the paranoid or the hacker and security communities.

"People have begun contacting us much more about encryption tools, whether it's the people who are inventing private-messaging tools and devices or people asking for comment on them from the press," said Seth Schoen, a senior staff technologist at the Electronic Frontier Foundation. "We've heard from people who've said that they were inspired by the Snowden revelations to create privacy tools. In that sense there is a definite uptick."

GoTenna's dual purpose

GoTenna pairs with your smartphone and lets you send text messages and location data through an app to other users of the device, which is why the gadget is sold in pairs. The messages are end-to-end encrypted using public-private key encryption, the company said, the same method that protects e-commerce transactions on the Internet.

The catch: GoTenna was designed for everyday consumers, but with some wiggle room. On one hand, it was meant to be a device that wouldn't have to rely on gadget-loving early adopters and would instead appeal more to people in situations like Gregg Berkholtz, a datacenter consultant living in Portland, Ore.

Though quite tech savvy, Berkholtz -- a regular backpacker who also takes disaster preparedness measures -- can't reliably use walkie-talkies. "Having a profound hearing loss, and with a cochlear implant in my near future, a method for reliable off-grid communications is high on my goals list," Berkholtz told CNET. That makes a smartphone text messaging device a no-brainer, regardless of encryption.

"Certainly the feedback that we're getting now is validating a lot of the assumptions that we were going on before," said GoTenna chief Daniela Perdomo. "It was interesting to see that even communities that aren't normally on the bleeding edge of technology buying GoTenna. But if you're solving a problem that is real to them, they're going to come out of the woodwork, whether it's a cabin in Montana or the wilderness of Alaska."

However, Perdomo, with the expertise of her brother and co-founder Jorge -- a systems architect and GoTenna's CTO -- figured that if they accepted Bitcoins and advertised the device's encryption perk, it might appeal to certain subsets of the crypto community. That would allow GoTenna to appeal to people like Levy who may or may not have a need for off-the-grid communication but are nonetheless interested in taking handheld encryption on the go.

"If you're solving a problem that is real to them, they're going to come out of the woodwork."

Daniela Perdomo, GoTenna CEO

"I definitely don't think there's one way to use it," Perdomo said. Though that makes GoTenna hard to market sometimes, she admits, it means that instead of being restricted to a few use cases, the device could be co-opted by all kinds of enthusiasts and used however they see fit.

The strength of the cryptography helps too. GoTenna uses 224-bit elliptic curve encryption, an advanced cryptographic algorithm that, depending on how it's used, can be safer than other, more standard methods like RSA. The company strengthened GoTenna's protection by using two-factor identification, meaning only those who can access the device associated with their phone number can begin receiving and sending messages using GoTenna. Furthermore, the app gives users the control, using public keys to encrypt messages but private ones to decipher them once they're received.

"This method allows each individual GoTenna user to have their own unique set of key ciphers," Jorge Perdomo explained in an email exchange with CNET. That's important because it means that hacking one GoTenna doesn't create vulnerabilities in every device. "In a way, even our encryption could be said to be decentralized," he added.

Update at 6:40 p.m. PT:Clarified that GoTenna does not rely on mesh networking to send messages from one device to another.

Update at 11:20 a.m. PT, Monday, Sept. 8: A previous version of this article said that GoTenna's platform contained a public API; the company has a SDK, not an API. A quote was incorrectly attributed to Jorge Perdomo when it should have been attributed to Daniela Perdomo.